Free-response channels are intended as lightweight chat surfaces — the bot
responds to every message without requiring an @mention. But the auto-thread
gate only checked DISCORD_NO_THREAD_CHANNELS, not DISCORD_FREE_RESPONSE_CHANNELS,
so every message in a free-response channel still spawned a brand-new thread.
That turns a chat channel into a thread-spawning machine: 1 thread per message.
The user-facing docs at website/docs/user-guide/messaging/discord.md already
describe the intended behavior ("Free-response channels also skip auto-threading
— the bot replies inline rather than spinning off a new thread per message"),
so this is a code-vs-docs gap, not a design change.
Fix: OR is_free_channel into skip_thread alongside the existing no_thread_channels
check. One-line production change.
Regression test added at tests/gateway/test_discord_free_response.py:
test_discord_free_response_channel_skips_auto_thread asserts that a message
in a free-response channel never calls _auto_create_thread. Reverting the
one-line fix causes the test to fail with 'Expected mock to not have been
awaited. Awaited 1 times.' — i.e. the test demonstrates the bug concretely.
d557544560